Is 115db dangerous for my hearing?

Discussion in 'Archived Threads 2001-2004' started by AlbertH, Jan 8, 2002.

  1. AlbertH

    AlbertH Stunt Coordinator

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    I love giving reference demos on my system (u571, fast and the furious, pearl harbor). I play it at reference level (85db on avia) and the volume goes all the way up to 115db+. How long should/could i listen to these levels without damaging my hearing in the longrun?
     
  2. ColinM

    ColinM Cinematographer

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    Won't take long...You lose a little bit each time.

    I have the figures at home. If nobody posts them, I will later.

    They are in the SPL manual...
     
  3. Ted Lee

    Ted Lee Lead Actor

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    isn't a jet engine something like 120db??? that should tell you all you need to know... [​IMG]
     
  4. ColinM

    ColinM Cinematographer

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    Standing under a jet, it's like 135ish.

    Rock Concert standing-in-front-of-the-stack while Townsend does the windmill is 120ish.

    - CM
     
  5. ColinM

    ColinM Cinematographer

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    Hours per day Sound Level (dB), A-weighting, SLOW response

    8 90

    6 92

    4 95

    3 97

    2 100

    1.5 102

    1 105

    .5 110

    .25 or less 115
     
  6. Tony Genovese

    Tony Genovese Supporting Actor

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    The 115db you're getting is the LFE. Your ears can tollerate it for the amount of time the film is putting it out although if it's low enough, your bowels might not. The other tracks peak at 105db.
     
  7. Robert Fellows

    Robert Fellows Stunt Coordinator

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    Yes
     
  8. Nick P

    Nick P Second Unit

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    I'm assuming the 115+ happens at dynamic peaks? Most of the movie would be much lower, yes? Peaks like that usually don't last long and all combined throughout the movie total less than 15 minutes I would think. Now if the entire two hour movie was hitting 115db then you would suffer damage.
     
  9. Dustin B

    Dustin B Producer

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    Like Tony says, the calibration spec is that the LFE channel can do 115 (by the way, what equipment are you using, in what size room, that you can hit reference bass levels?) and the other channels can hit 105. Also remember that human ears are most sensitive to the frequency ranges that comprise human speech.

    You most likely took a C weighting measurement, try it again with A weighting (human speech frequencies). As long as the SPL level stays at or below 90dB except for the brief action sequences (they get up to over 100-105) you should be fine.

    I read somewhere that human ears can tolerate subwoofer type frequencies at over 120dB without a problem. But once you get up to frequencies in the 1000-8000hz range going over 90 for more than a couple hours everyday will result in damage. Mind you I don't know for sure if that is true or not, so I don't plan on listening to 120dB bass (assuming I could even produce it) for more than a few seconds at a time).
     
  10. ColinM

    ColinM Cinematographer

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    Dain Blammage...
    I can't hear the birdies!
    [​IMG]
     
  11. AlbertH

    AlbertH Stunt Coordinator

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    I am in a 13x17 foot room, i am running 4 jbl nd310s (2 front and 2 rear) a jbl n-center, a jbl pb12 (250 watt) and infinty bu120 subwoofer (150 watt) (both 12") stacked on top of each other in the rear of the room, all running off of Yamaha HTR-5280 (110 watts per channel), with a Toshiba 50h81 (i know the tv doesnt matter [​IMG] ) For all you math wizards that means i have EIGHT 10" WOOFERS and TWO 12" SUBWOOFERS!!! At the time i took these measurements i set my fronts and rears to large and bass to both mains and woofer, but have since changed it to small speakers with bass routed only to the woofer after hearing tips to other users. Does my 115db level seem reasonable??? BTW i did measure with the ratshack spl meter.
     
  12. Dustin B

    Dustin B Producer

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    Well according to the spec, it's only the LFE channel of a calibrated system that should pass 105dB. So that 115 dB should be coming just from the two subs. The room is fairly small so that will help a lot.

    Also it would probably take 4 of those 10" drivers to equal the output of one of your subs. And that would only be above 35-40hz. In the 25-35hz region those towers will have very little output, and below 25hz your subs will have very little output.

    The other thing is that on low frequencies the RatShack meter is inaccurate, it usually reports a number that is too low. Which means your actual level could be 1-3dB higher in the frequency range your peaks are happening.

    Take the reading again using an A weighting. If you are still getting 115 dB then yes that will likely be damaging to your hearing. I don't think an A weighting reading should pass 105dB.
     
  13. Jason Wolters

    Jason Wolters Stunt Coordinator

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  14. Dustin B

    Dustin B Producer

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    For reference, I got a Rat Shack Digital meter for Christmas this year. I'm still waiting on A&B to get me and AVIA disc in (I managed to talk them down to $55 CDN from $75 CDN with very little effort) so I don't have my system calibrated to reference level yet.

    All I've done is calibrate all the channels to the same level using my Onkyo receivers test tones. The sub is just under 10dB above the rest though. Then I set the overall volume level to what I find comfortable for each movie.

    Anyways, onto the point. I played The Phantom Menace THX intro and watched the SPL meter with a C weighting. Hit 103dB at my listening position (for some reason I don't think I'm gonna be listening at reference levels). Then I played it again (without changing any volume settings) with the SPL meter on A weighting. The level didn't pass 82dB.
     
  15. Jason Wolters

    Jason Wolters Stunt Coordinator

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    Right. Because with the meter set to A weighting you are measuring NOISE level. Whereas with the meter set to C you are measuring SOUND level.
     
  16. Tony Genovese

    Tony Genovese Supporting Actor

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    Also, with regard to the reading with the Radio Shack meter, chances are you have some rather large peaks below 80 caused by room eigentones. These are specific to certain frequencies. Since your Radio Shack meter can't distinguish the room generated peaks, your overall sound level is probably lower than you think. And again, subwoofer frequencies are not going to damage your hearing at the levels presented. It's the higher frequencies that cause the problems.
     
  17. Ray R

    Ray R Stunt Coordinator

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    Hi Jason,
    Not doing much at work either? [​IMG] I read your follow up in the other thread. The radio shack manual incorrectly implies that noise level means "A" scale and sound level means "C" scale.
     
  18. John Tuttle

    John Tuttle Agent

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    120db with sub frequencies should not cause any major damage. I used to drive around listening to my music fairly loud in my mini truck for a few years. Levels in the truck were usually in the 150db range.
    And yes, I would listen to a constant tone just to feel the bass. Or play songs, either way, it moved whatever was in (or out of the truck).
    Could this be why I believe my system at home is not loud enough? Maybe I need 4500watts to my subs like I had in the truck [​IMG]
     
  19. BruceD

    BruceD Screenwriter

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    The story on SPL goes something like this:
    Workplace
    US Dept of Labor standards for allowable volume in the workplace is:
    The table Colin listed which is measured with and uses the "A" weighting scale for it's compliance with standards.
    This scale uses a measurable frequency response between 500Hz-10kHz.
    As you can see, not suitable for calibrating speakers, but very useful for seeing how much damaging SPL you are subjecting yourself to.
    Because the ear has a graduated sensitivity curve (called the Fletcher-Munson curve - less sensitive to lower frequencies means you can tolerate higher SPL levels of bass) also means frequencies above 500Hz to maybe 4000Hz+ are the really dangerous frequencies for high SPLs.
    Home Theater
    Calibrate with the "C" weighting scale which uses a measurable frequency response between 32Hz-10kHz.
    By the way if you change the scale while measuring the movie you're watching (especially an effects oriented section), you will see at least a 10dB difference between the readings. The "A" scale will always be lower when bass is present in the measured signal.
     
  20. NickSo

    NickSo Producer

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    Nick So
    Just learned in school today... 85dB+ volumes for extended times can cause hearing damage. The louder the volume, the faster it takes to damage your hearing
     

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